function changeImg(){  
  var imgSrc = $("#imgObj");  
  var src = imgSrc.attr("src");  
  imgSrc.attr("src",chgUrl(src));  
}  

//时间戳  
//为了使每次生成图片不一致，即不让浏览器读缓存，所以需要加上时间戳  
function chgUrl(url){  
  var timestamp = (new Date()).valueOf();  
  if((url.indexOf("&")>=0)){  
    url = url + "&timestamp=" + timestamp;  
  }else{  
    url = url + "?timestamp=" + timestamp;  
  }  
  return url;  
}  
   

